An Early Christian site founded by St. Ciarán in the mid-6th century on the eastern bank of the River Shannon Co. Offaly. The site includes the ruins of a cathedral, seven churches (10th -13th century), two round towers, three high crosses and the largest collection of Early Christian grave slabs in Western Europe. The original high crosses and a selection of grave slabs are on display in the visitor center.

This arch is known as the Whispering Arch because the monks held confessions there. A monk put his ear at the corner of the arch and the sinner talked into the corner of the other side of the arch.